Transmission system



Aug. 2'7, 1935. s, DQBA, JR 2,012,810

TRANSMISSION SYSTEM Fild April 30, 1952 I 2 3/ INVENTOR v 'S.DOBA,JR.

ATTORNEY Patented Aug; 27, 1935 Stephen Doha, Jn, "'Bell 7 Telephone This invention relates. to signal transmission "systems and .particularlyto circuits for control- 'ling the energy, volume of signals. on transmission systems. 5." a

'One-"objectof the invention is to provide a ing a hangover-in the operation thereof to raise the energy gain onthe transmission line and by a second marginal 'means having a hangover in the operation thereof to limit the increase'of the energy gain on the transmission line.

Another object of the invention is to provide a transmission system having gain control Imeans in a receiving channel and-gain ;control means in a transmitting channel with a control. device that shall jointly operate the twogain control other channel.

Another object of the invention is to provide a transmission systemhaving gain control means connected to a transmission line that shall control the gain control means to raise'the energy gain on the line according to the peaks of the transmitted signals and that shall control the rate at which the energy'gain is efiected. i

A further object of theinvention is to provide a transmission system having gain control means in a transmitting channel and gain control'means in a receiving channel with gain increasing means for controlling said gain control means to raise the gain in the transmitting preventing operation of the on said channels beyond predetermined limits and gain decreasing means for controlling the gain "control means to lower the energy gain in the transmitting channel and to raise the energy.

gain in the receiving channel that shall insure operation of the gain preventingmeans and prevent-operation of the gain decreasing means when the receiving channel is in operation. v In signal transmitting systems it is desirable and in somecases essential to control the energy volume of the transmitted signals.- In transmit-1 on the line to raise the trol devices inthe transmitting condenser." v g 5 any extentthe gainIeffected by thegainoontrol 7 channel while lowering the gain in the receiving channel, means for a gain increasing means varying the energy level receiving channel is raised.

New York, N. "Yaassig iior to Laboratories, Inc01'porated, V New York 'N. Y.,' a corporation I Application April 30, 1932,

' j 19 Claims. (01.17344) V of'New York seriarNo, 608,362

ting radio vbroadcast programs-i rover, transmission lines itis e'ssentialto control the volume of the transmitted programs to prevent overloading the various apparatus onftheZl-ines"such-as' repeaters; In theitransatlantic radio system, it

is necessary to hold the .energy. volumeqon other system in front! of the. radio transmitterswithin .-a limit' whichtwill not overload the-transmitter; This application'is'i animprovement over the transmission system disclosed in the: patent to "John LxHogg andrstephen Doba'gJr; No. 1,-. 853,974; dated April 12; 1932. .1 v

.In the system employed to describethe inventiona' gain .controlfdevice which may be called a variorepeateris connected to the transmitting channel and another gain control device ;;isconnectectto the receiving :channel. Ihe gainhcon trol device in thejtransmitting channelcomprises twothree-element space discharge devices in push-pullxrelation and connectedfl efiectively in seriesxwiththe transmitting channelli -The gain 'commldevice inihe' i ingchannelcofi prises two'three-element space discharge devices connected acrossgthereceiving channel. 0 A re-5 'sistance element is connected across-- the space discharge devices" connected to channel to, limit thegainvariation that :may be effected in the-receiving'channel. -'I-he"gain coni r and receiving channels are jointly-pperated so that again in :one channel wfllbeeccQmp-anied by; a .l s f n h other channel. ,'I'he;, gain control device in the transmitting channel is so controlled as to main tain a-,constant volumeone-the channel beyond the gaincontrol devicet'v V V The potential onj the 'grids of: the space. discharge devices-comprisingth'e gain-control ,de-r

vices in the transmitting and receivingchannels the receiving 7 is controlled in accordance with thelcharge onaa p When the I condenser" is charged "to device in the transmitting channel is loweredasi set forthiinlthe above mentioned patent to John L. l loggand Stephen Doba,'Jr.'I Atthesame time the gain eifectedby the gain controldevice in the The chargeonjthe condenser is controlledby three separate circuits, again increaser circuit;

: a gain increase disabler circuitfand a gain de creaser circuit." The'gain increaser circuit is operated at the commencement of communication when the peaks of speech current on the transmitting channel beyond the gain controlidevice are belowa lower limiting value andtthexpeaks of; the speechton-the transmitting channel before 5 controls the "disc the gain control device'are above the peaks of speech for a weak talker; The gain increaser cir-" cuit includes a gas-filled tube which operates in amanner of a marginal device for controlling a relay which in turn establishes a circuit for discharging the condenser. In the outputjcircuit of the gas-filled tube are connected means com- 1 prising capacity and resistance elements for producing a hangoveractionin' the operation'of the relay controlled by. the gasfilledtube'. The gainincreaser circuit is controlled from the transmitincrease disabler circuit is controlled channel at a point beyond comprising capacity and resistance elements are providedin the' output circuit of the gas-filled tube in thegain increase disabler circuit .for V I the operation of the establishing} a hangover in relay controlled by the gas-filledtube. 1 The gas filled tube in thegainincrease disabler circuit is,

operated drtriggeredoff 'whenthe peaks of the speech current on'the transmitting channel beyond the gain trol device are above a lower limiting value. f

The relay inlthe gainlncreaser circuit, which arge of the condenser, effects discharge of the condenserthrough av number of resistance elements.

elements included in the discharge circuit for the condenser is'variedjbya rate control relay in order to vary the'ra'te at which thegain'on the transmitting, channel is effected; The rate control relay is operated in accordance with the "space current flow throughthe space discharge devices comprisingthe gain control-device on the transmitting channel. "Without variation in the amount of resistance invthe condenser discharge circuitlthe gain in the .transmittingchannel would be very rapid at first and then become relatively slow. In order-to insure a more uni- .form rate. of gain in the transmitting channel, the resistance elements includedjin the condenser spacedischarge circuit are varied by the rate control re ay'in accordance with the space current flow through the space discharge devices comprising the gain control mitting channel. 1 Q g f r The 'gain'd'ecreaser circuit is controlled from the transmitting channeljat a point beyond the gain control: device. "and serves to charge the Jabovi'mentionedcondenser whenthe pealrs of "speech'current beyond thegain control device in the transmitting V channelrise above an upper The gairi' decreaser' circuit. cornbiased push-pull detector having limiting value. prises a hi hly the output circuit thereof permanently connected across the control condenser. Whenever the output on the: transmitting channel exceeds a predetermined upper limiting value the gain decreaser circ t is actuated and the control condenser is charged. to impress a' negative bias to' the .gridsof the gain control device in the transmitting" channel an potential is-impressedon the grids of the control device in gain ', the receiving channel isinuse. w preferably is operated by the echo suppressor circuits (not shown in half the Thegain increase dis- The number of resistance 7 device on the transtransformer I.

. nel. Batteries 2'2, and23 d a similar negative biasing V the receiving channel. This fres'ults in"a"continually decreasing gain in the transmitting channel until the output in such channel falls below the operating value for the gain decreaser circuit. In operation the gain decreaser circuit is operated by the peaks of voice current. r

Means arev provided for preventing operation of the gain decreaser circuit and to insure operation of the gain increase disablercircuit whenever Alrelay which detail) serves, when 0perated, to establish a short circuit around onetransformer secondary winding connected to the two detector tubes in the gain de- "cr'eas er circuit thusto disable the gain decreaser circuit and prevent any increase in the charge on the control condenser when the receiving channel 'is'in use. The relay controlled from the receiving channel when operated from the receivin cnannm also serves to remove the bias on'the' gas-filled tube in-the gainincrease disabler circult so that the gas-filled tube'is operated to effect operation of. the relay controlled thereby condenser by the gain increaser circuit. 'i'

The single figure in the accompanying drawing is a diagrammatic view of gain control circuits constructed in accordance with the invention.

Referring to the drawing atwowire"system and thus prevent any discharge of the control (not shown) is connected in any suitable manner to a four-wire system comprising a transmitting channel I and receiving channelZ. The transmitting channel 1 comprising conductors? and 4 has a vario-repeaterconnected thereto for controllingthe gain in energy'and accordingly the volume of the'transmitted signals. The variorepeater comprises a second control devicea, an amplifier l and an amplifier 8.- The gain control device 5 comprises two three-element space discharge tubes 9 and H) which are connected in push-pullrelationship andin series with the line. The input circuit or the gain control device 5 is connected to a transformer H; Impedance means 12 is connected across the'primary winding of the transformer'l l. Theoutput circuit of the gain control device E is connected by transformer i3 to the gain control device 5. Divided impedance means i4 is connected across the primary winding of the transformer 13.

The gain control device 6 comprises two space discharge tubes!!! and is which are connected in push-pull relationship and in series with the transmitting channel. The output circuit of the gain control device circuit or" the space discharge amplifier l by a The amplifier I is connected to the amplifier 8 by means of a transformer '18 and the amplifier 8 is connected to the transmission line by means of a transformer I9.

8 is connected to the input gain control device 5, a

,A battery 26 is provided for supplying heating current to the filaments of the tubes 9, iii; l5 and i5 and theamplifiers l and 8. is provided for supplying space current to all the space discharge devices in the transmitting chanpressing negative grid potential on thetubes 9 and. lcand l5 and [6 which comprise the gain control devicesfi and 6. The potential impressed upon the grids of the gain control devices 5 and E5 is also controlled in accordance with the charge ona control condenser "28 as will be described hereinafter. is connected across the output circuit of the gain control d evice 6 for adjusting the gain in the are provided for im-' 'An adjustable impedance means 25' A battery 2! transmittingfl channel at Will -An*impedance means 26-is connected in thespace'current path for the tubes comprising'the gain control devicefi. The I A drop" across the-impedance means "26 is utilized for controlling the operation of a gain rate relay 21 to govern" the rate at which the gain :increasetakes place, as will be described hereinafter; Althoughgtwogain control devices 5 and Bare shown in the transmitting channel T, it is to be understood that only one'ormo're" than two gain control devices may be used if so as: sired. hi irthermore, although the gain rate re lay 2;! isillustrated as controlledby an impedance means connected inpircuit. with the gain'conitrol deviceti, it may also 'be'controlled in accordance with thesp'ace current flow throughthe gain conima and 28 in the filament heating circuitsfor' the 'arn'plifiersljandfi are provided for impressins biasing potentialontlie grids of theamplifiers 'iandEL' f The receivingchan el 2 comprising conductors and .39 includes a gain control. device 3 l, i The gain control" device 3! comprises two three-element space discharge tubes"32"a nd 33 which are connected across the conductors of the receiving channel. The gain control device 3! is con ing channel. A. battery His provided fori'supply- 1 ing plate current to thespacedischargetubes 32 and 33' andla battery "45 is provided. for heating thefilaments of the tubes 32 iandl3 3. epotena tial on the grids ofthe tubes Hand '33 compris ingthe gain control-device 3l';is controlled.) in

accordance with the charge on the icon'trol, con

denser 25 the samemanner asthe potential on the grids" of the tubes in the gain; controlde vices 5 and 6 is-controlled from thevcondenserlz't.

5 The charge on. the control condenser T24 is governed by a gain; increaser circuit ,46, fafi'gain increase disabler circuit and again clecreaser circuit-J8, The gain increaser circuit comprises amplifier space discharge device ifliara-three element gas-filled tube-r5lisand a-relay 5|. The

input circuit 01f the amplifier; 49 is'connected to the-conductors '3 and 4 of'sthe ,;transmitting channel ata point before the gain control devices 5 and 6 j by means of a transformer 52. Capacityand resistance elements -are preferably connected to the windingsoi the transformer-5i for tuning the circuit to audio frequencycurrents. The output circuit of the amplifier-dais; connected by; a transformer 53 to the in1: ut circuit of:.the gas-filled tube 50. The gas -filled tubej!) is preferably filled with arr inert gas-and operates asja marginal device to effect operationof-jthe relay 5 [when predetermined peaks of, energy are transmitted over the transmitting channel.- I I A battery54- is.:provi ded forsupplying plate potential to the amplifier 49,and the gasfilled 'tube 56. The battery 54 also supplies current for energizing the two windings 55and' 55 f the relayi; A battery 57 provides heating current for the filaments of the amplifier 49 and the gas: filledztube. 50. Biasing potential-for the gridof,

trol device 5, if so'des1red. Re sistance elements 57. 1 The amplifier is filled tube 66.

gthe battery 'li andserves to hold the 49 provided by the drop element 58. A batterym59 the amplifier tube across a resistance supplies biasing potential: for the grid of the gas- The winding 55 of the relay 5| is connected across thebattery 54:for biasing the armatureiiflof therelay 5| away from the-contact member 6 I and to the position shown in the drawing. The Winding 56 of the relay 5i is connected across the battery 54' incircuit with a'resistance element 62 and the gas-filled tube 59. Accordingly,

the Winding 55- of the relay Elwhich moves the contact with the The gas-V armature 60into' engagementwith the memberB! is controlledin accordance impedance of the gas-filled tube 5! 151 filled tube is marginal in operation and triggers oiT when predetermined peaks-of energy are impressed upon the'transmitting channel conductors 3 and 4. I A hangover circuit comprising acondenser 63' and a resistance'element 64 is connected across the gas-filled. tube 58 in order to 5| by the gas-filled tube. The condenser-63 is charged from the;battery 54 by the circuit including the winding 56. 7 Upon operationgof the gas-filled tube 56 the condenser53 is discharged through the space discharge path the tube,

stopped,the relay 5I'is notiimmediately released, but a hangover in' theoperation thereof ispro vided according -to .the' time required to recharge the condenser 63.

The gain increase disablercircuit 41 comprises an amplifier 65 preferably of the three-element thermioniotype, a gas-filled tube; 66 which is provided by When theiimp'edance of thegas-filled tube is raised and current flowing therethro-ugh is provide a hangover in the operation of the relay i preferably of the three-element type and a relay connected to the trans-. mittin'g'channel lat a point beyond the amplifier 8 by means of a transformer tti. A potentiom eter 69 is provided in'the input circuit of the amplifier 65 for'adjusting the operation of-the gain'increasedisabler circuit. The output aircuit of the amplifier tubes'65is connected to the input circuit of" the gas-filled tube 66 by means of The output circuit of the gasa transformer. 79. filled tube 66. is connected to a winding"?! of the relay 67; A battery 72 is provided for supplying platepotential to the amplifier 65 and thegase 7 Battery 13 isprovided for supplying. heating current to therfilaments of the amplifier 65 and thegas-filled tube 66.. Biasing potential forthe grid ofthe amplifier, tube is provided by the drop across theresistance' element Min the filament heating circuit.

:Biasing potentialior th'e; grid. of" the gas-filled j tube 66 is provided-bye, battery J5 in the gain decreaser circuit which is opposed by a battery 76. I'I'he battery 15 isassumed to supplynegative potential of approximately 67volts and theb-at- 'ery' 16 to supplya positive potential of approxi} that substantially negative mately 22 :volts, so biasin potential of grid of the gas-filled tube 65.

45 -volts is impressed on the The circuit of the batteries 15and 16 for supplymgbiasingpotenhereinaiter disclosed:

wi-The relay-61comprisesnot onlythe operating winding! I but abiasingwinding '58, i The biasing" tial to the grid of the gas-filled tube 66' is'controlled by a receiving'relay IT inamanner to be winding-- 78 is connected 1 across the terminalsof armature lii in engagement with a-contact member 8B.- When the operating winding 'llis energized the arnia V lture i9eismoved into ,engagement ith the con of the relay 61.

nel. beyond thei'gain' control tact member 01:. connected across the battery I2 The operating winding ,l-i I- is in circuit with a resistance element 82;.and thegas-fil-led tube 69..

The gas-filled tube 65is marginal inits operation the same as the gas-filled tube 50 in the gain increaser circuit 46.. The gas-filled tube 66. in the gain increase dis-abler circuit is assiuned to operate or triggeroff when the peaks of speech in the transmittingchann'el beyond the gain control devices are above alower limiting value. The gas-filled tube 50 in V assumed to operate or trigger ofiwhen the peaks of speech in the transmitting channel before the gain control devices are above those of a very A hangover circuit comprising a weak talker. I condenser 82a: and a resistance element 83 .is

provided in, the output circuit of the gas-filled tube 66 for effecting a hangover in the operation in a manner similar to the hangover circuit de-. scribed when reference was made to thegas-filled tube50; I r 1 h "The gas-filled tube 96 in the gain increase disabler circuit is operated not only according to the peaks of energy onthe transmitting chandevices, but may be operated by the relay. 'I'Ifwhich is controlled from the receiving 'channela'i'when the relay H is operated the circuit fromthe batteries. and- It for supplying potential .tofthe grid ofthe gasfilled. tube vis'opened. Accordingly; the strong negativebias on the grid of the gas-filledtube 66 circuit of the detector tubes wand 81 by means. of a transformer 90. Heating current for the thermionic type and 81. Atransformer .84 is provided for connecting rent tothe biasing -to be hereinafter set forth;

is removed to permit operationof the gas-filled tubeand operation of therelay 61;

The gain decreaser circuit 48 comprises an amplifier 85 preferably of the three-element two detector tubes 86 and the input circuit of the amplifier 05. to the'trans.

mitting channel at'a point beyond the gain control devices '5 and 6 and the amplifier 8. A potentiometerl89 is provided in the input circuit of the amplifier 85 for adjusting the operation of thegain decreaser circuit. The output'circuit of the amplifier 85 is connected to the input filaments of the amplifier 85 and the detectors 86 and 81 is provided by means of the battery 9 I.

A battery 92'is provided for supplying plate potential to the amplifier 85 andfor supplying .cur-

winding-93 of the relay TI. The operatingwinding 94 of the relay' 'I'I is controlled from the receiving channel in a manner Biasing; potential for the grid bf theamplifier 85 is supplied by sistance element I02 is excluded the gain increaser circuit is ve ation This hangover circuit operates a resistance element control condenserj24 for impressing potential on discharge devices I0, I5 and I6.

and 01 is supplied by a battery 'I5 which also controls the biasing poten-f charge devices I5" and 24 in accordance-with the operation of the detector tubes winding 98. The biasing winding is energized from the battery 54 and normally holds the armature 99 in engagement with the-stonmember I00 and away from v a contact member IN. The operating winding 91 which is energized according to the drop across the resistance element 26 serves to move the armature intoengagement with the contact member IOI. -When,the armature 99 of the relay is in engagement with the contact member IN, a refrom the discharge circuit of the control condenser 24 as will beset forth hereinafter. I

7 Assume afcharge on the control condenser 24 to be started on the transmitting channel sothat the peaks of speech before the gain control devices 5 and 6 are above the peaksofthe weakest talker and the energy peaks beyond the gain control devices are below the lower limitingvalue. Under such circumstances,

' the gas-filled tube 50 in the gain increaser circuit 46 is triggered off for completing a circuit through the operating winding 56 of the relay 5I. The condenser 63 in. the hangover circuit is discharged, the relay 5I" is operated and the armature is moved into engagement with the contact member 6|. Theengagement between the armature. 60 and the contact member 6| serves to complete a discharge circuit for the control condenser 24 through the resistance element I02 and I05. The circuit of the the grids of the gain control device 5 may be traced from the grid of the space discharge device 9 through portionv of the. secondary winding of the transformer II,'battery 22,condenser 24 and ground to the filament of the space discharge device 9. Similar circuits may be traced for the I The V condenser 24 is also connected to control the potential on the grids of-.the space discharge devices 32 and 33 in the receiving channel, i

The circuit completed by the relay 5| extends fromone terminal of the control condenser 24 throughthe armature of the relay 5I, contact member BI, resistance elements I02 and I05, contact member 80, armature 19 'of the relay 61 and ground'return'ng'to the other terminal of the condenser 24. It is thus apparent the resistance elements l02 and I05 areconnected across the condenser 24 for eifecting a discharge of the condenser. The discharge action on the condenser reduces the negative biasing potential on the grids of the which is effected. At the same time the potentialimpressed on the grids of the space discharge devices'32. and 33 comprising the gain control device in the receiving channel is reduced to reduce the gain eifectedin the receiving channel. It} may be noted that theresistance element 43 connected across the gain control device in the receiving channel serves to limit the control of the gain in the receiving channel, so that a certain gainin the transmitting channel is not accompanied by an equal equivalent loss in the receiving channeL' Whenthe space current forthe space dis- I6 comprising the'gain control device 6 is raised to a predetermined point; the relay'2'l is operated'to exclude the resistance element I02 from the dischargecircuit of the condenser 24. The relay 21 is provided in order toeffect a more uniform gain of energy in the transmitting channel.- If the relay 21 were not provided, the gain in the'transmitting channel would be very rapid at the beginning of the discharge of the condenser 24 and then be-' come relatively slow." The excluding of the resistance element I02 from the discharge circuit gain control devices 5 and 6 in' the transmitting channel to increase the gain disabler circuit.

with the contact member 8| .,.This 'breaksthe discharge circuit for the, condenser 24 and prevents further increasein the gain on the transmitting. channel. .Wher'i the armature: 19 of the relay .61 engages condenser 88 efiectively'shunts' a: portion of the impedance in the input circuitofthe amplifier 65 to increase the sensitivity of the gain increase 'When the gas-filled tube. 66 andthe gain increase disabler-.-circuit cease to operateby, reason of the peaks of the gain control devicein the transmitting channel falling below the lower limiting value, the relay 67. is held operated for a limited'period by reason of the hangover action condenser 82: and the resistance element 83. 1

If the peaks of speech on the transmitting channel beyond the gain controldevices 5 and 6.

and the amplifier-8 rise above the upper limiting value, then the negative potential impressed on thegrids of the detector tubes 86 and 81 inthe gain decreaser circuit isiovercome to permit current flow through the detector tubes and charging of the controlcondenser'fl. The chargeon the condenser 24 serves to impress negative biasing potential on .thegaincontrol devices 5 and '6 in thetransmitting channel and the gain control device 3| in the receiving channel. The operation of the control condenser in governing the gain on the transmitting and-receiving; channels is the same as the control disclosed in the above mentioned patent to JohnL-Hogg and Stephen Doba, Jr, .1 a p In case the receiving channel is-in operation and the. transmitting channel-is idle,'it is desirable to have the chargeh'eldonthe'condenser'24 and to permit no change in 'the se tting of the gain control devices in the transmitting channel. The echo suppressor circuits? ")1: serves to eifect ener gization of the winding of the relay [1 whenever the receiving channel is in use. ,Thus the armature Hi8 of the relay 11 is moved from engagement with the contact member :l09 into engagement with the contact member I [0 whenever the receiving channel is. in use. 'Such movement of the armature J98 serves .first'to'break the cir-'- cuit of the 'biasingrbatteries' 16 andrlli for con trollingthe potential impressed onthelgrid of the 1 gas-filledtube 66in thegain increase disabler circuit. The gas-filled tube 66.is operated to efiect operation of the relay 61.. The relay'fil opens the discharge circuitfor the"control con denser 24 and prevents any discharge of the con denser'24-l The engagement of the'armature I08 of the relay 71 with the contact member I I0 serves to short-circuit one-'halfthe secondary winding of the transformer connected to the detector tubes 86 and 81 in the gain decreaser circuit 48f. This serves to prevent any operation of the detector tubes 86 and 87 and accordinglyto prevent any in-' crease i-n-the charge on the 'condenserflwhen' the receiving channel is in use-J the contact. member 8|, thespeech beyond produced by the Modifications in thesystem andin the arrange ment' andlocation of the spirit and scope modifications are intended .to belcoverediby ithe appended claims.

What is claimed is: 1. In a signal system; a transmission line, a

gain controldeviceconnected to the line for controlling thevolume of thetransmitted signals,"

means comprising a gas-filledspace discharge device having, an anodeand a cathode and which suddenly becomes operative when the energy level on the line bfore'said gain controldevice exceeds the peaks of the weakest talkers-control means quickly operated by said; gas-filled space discharge device for increasing the ga n by the 'cuit of gas-filled device for eifecting a' predetermined hangover in the operation of said control meansby said gas-filled device; Q l

2. In a signal system, a transmission line, a gain control device connected to the line for con-,

trolling the volume of the transmitted signals,

comprising a gas-filled controlled according to s before the gain control device and a relayz'controlled by said'gaS- filled of said gas-filledldeyice for'Iifecting a hangover in the operation-of said relay; gainfp'reventing' parts may be made within of the invention, and such means comprising agas filled space discharge de vice controlled according to the volume on the controlled by said last mentioned for preventing increase in the gain determined level by the gain control deviceand above a pre a condenser anda resistanc elementlcohnected to the output'circuit of the'gas-filled device in the gain preventing means for'effecting a hangover in the operation of the last mentioned relay.. 1 3. In a'signaljsystem, a

transmission line, a

gain control deviceconnected to the'line for con-' transmitted signals,

weakest talkers to increase the' gain effected therebyjand means comprising a condenserand aresista ncejelement in'circ'uit with said marginal device to produce a hangover in the element in series across the outputlcircuitfof said gas-filled device foreeifectin'ga hangover in the operation of said relayfgain preventing means comprising ajgas-filled space discharge device controlled according to the energy volume on the line beyond the gaingdevicej and a relay for pre venting increase inthe' gain bythe gain device above a predetermined leveland a 'co'ndenser and a resistance element in vseries across the output circuit of the ga's-filled device in' the gain pi-e control device, and a relay quickly operated by said gas-filledspace discharge" device when the energy level on the line exceeds the peaks of the weakest talkers for increasing the gain by the gain 1 control deviceja condenserand a resistance elementgconnected across the output circuitof said gas-filled device for effecting a hangoverin the 7 operation of said-relay, gain, preventing means comprising a gas-filled space discharge device controlled according to thevolume on the line beyond the gain control device and a relay for preventing increase in thegainabove a predetermined level by the'gain control device, a condenser and a resistance element connected across the output circuit of said last mentioned gas-filled device for efiecting ahangover in'the operation of the last mentioned relay, and means controlled according to the volume onthe line beyond tliegain control device for controlling the gain control device to lower the gainfeflected thereby.

6. In a signalv system, a transmission ling. a

vacuum tube gain controlidevice connectedtothe line ior controlling the volume of the transmitted signals, means ior'impressing a negative potential on the grid of said gainco'ntroldevice according to the energy volume on the line beyond the gain control device;fgain increasing means comprising a 'gas-tfill'ed space discharge device controlled according to 'the energy volume on the line be.-

fore the gaincontrol device and a 'relay quickly operated by the gas-filled tube for'inc'reasi'ng the resistance element, 'gaini'n creasing means gain bysaid gain control device if the energy level on the line before the "gain device exceeds the peaks of the weakest talkers and the energy level on the line beyond theigain device isibelowa pre determined level, and means comprising a condenserand a resistance-in the output circuit of said gas-filled tube for effectingahangoverin the operation of said relay b'y the gas filled tube.

"'7. Ina signal system, a transmission line, a

vacuum tube gain control device connected-in series with the line ,forvcontrol ling the volume ofthe"transmitteqi ignals means comprising a condenser for impressinga negat the'grid'o'f 'lthegainidevice to, lin '1it the gain, a-

controll-ed according to tl'feenergyvolume on the line before saidgain device for completing a circuitthrough said resistance element to discharge said" condenser toincreasethegain of the gain device) and rnea'n'spc'o trolled according to the space currentof the gain devicefor varying the value ofsaidfr'esistancef element incircuit with thecondenserto:control the rate of gain by the gain device. p v i8. In a transmission system, transmitting and receiving channels; again" control device connected to said transmitting 'channel, control means for-governing said 'gain'control deviceto increase the energy volume of signals on the line to a predetermined level, gain preventing means operated from thetrfnsmitting channel when the energy is 'abovea; predetermined level for preventing increase in the energy of "the signals by said control means, gain decreasing-means for controlling the gain control device, to lower the yond the device 1 is ive potential on on the transmitting gain'on the receiving channel, and means autowhen the receiving channel 60 fgain'riieffectedi thereby;iand 'meansautomatically operated when the receiving channel is in use "for operating said again preventing Lmeans andilfor preventing operation of the gain decreasing means....;;

a J 9.j;1n. airansmissionisystem, transmitting and receiving channels, a variable gain control device connec'tedlt'o"saidtransrmtting channel, gain in'-.

creasing means, for governing the gain 'control de- Vice to effectlincrease in the gain thereby, gain 10 preventing -means operated when the energy beabove a predetermined level for preventingroperation: of said gain increasing ,n'ieans toincrease the g'aimgaincdecreasing means -for ;contro1lingthe. gain control device to lower 15 the gain, and means controlledfrom the receiving channel whenzthefreceiving channel is in use for edisablinglth ergain decreasing means and for operlat'ing the gain preventing means 1 '1 10, Inatransmissio'n' system; transmitting and 20 receiving channels, a three-element vacuum tube variable gain control device connected tosaid transmission 'channel,;a condenser for controlling theygrid potential on the gain control device to governpthe gain effected thereby according to the 5 "charge on the condenser, gain increasing means for controlling the 'charge'o'n said condenser'to increase the gain'by the gain {control device; gain preventing means for preventing control of said gain increasing means to in- 30 condenser bythe N crease the-gain above a predetermined amount,

" gain decreasing means forcontrolling said condenserto lower the gain effected by the gain-control device and means automatically operated when the receiving channel is" in use for pr'eveht- 5 i'ng (meration oithe gain decreasing means and forfop'eratingjthe'gain'preve'nting means.- I 11. 'In a 'transmission system, transmitting and receiving channels, two three-element vacuum tubes connected in' series with said'transmitting 40 channel for controllin'g i-thagain therein, two

three eleznent vacuum' tubesfconnected across the I receivingcliannel for c'ontrolllng the gain therein, a condenser for controlling thegrid potential on the gaiii' control' tub'e's connected to the trans mitting and receiving channel's,flg'ain control means governed by the energy volume on the transmitting channel for, controlling the charge on said condenser to increase the gain on the transmitting channel and decrease the gain on'the receiving channel, gain preventing means governed by the energy volume'on the transmitting channel for preventing controlof said condenser by the g'ain control means; gaindecreasing means operated when the energy peaks on the trans- 55 mitting channelare above a predetermined level for controlling said condenser to lower the gain channel and increase the matically operated is in :use for preventing operation of said gain decreasing means and for operating the gain preventing mean's. l 12.'In a signal system, a transmission line, a

gain control device connected to the line for con-' p trolling. the energy volume of the transmitted signals, control means governed according to the energy volume on said line for controlling said gain control device toincrease the gain on the line, and means, automatically-governed by the operation of the gain control deviceiforcontrolling the rate of gain efiectedby-the gain control device under. control -of the control means.

'13. a signa1,sy,stem,pa transmission line,

a vacuum tube gain c'ontroljdeviceconnected ei- W device to increase-the 7 2,012,810 Iectively in series with the line for controlling the energy volume of the transmitted signals, control means. governed according to the energy volume onisaid line for controlling said gain control device to increase the energy gain on the line, and means automatically operated according to the space current of said gain control device for governing the rate of 14. In a signal system, atransmission line, a gain control device connected to the line for controlling the volume of the transmitted signals, gain increasing means governed according to the energy level on the line before said gain control device for increasing the gain by the gain control device, and means automatically governed by the operation of said gain control device for controlling the rate of gain effected by the gain control device under control of the gain increasing means.

15. In a signal system, a transmission line, a

three-element vacuum tube variable gain control,

connected effectively in series with the line for controlling the volume of the transmitted signals, means for impressing potential on'the grid of said gain control device according to the energy volume on the line beyond the gain device device to limit the gain, gain increasing means comprising a gas-filled space discharge device and a relay controlled according'to the energy volume on the line before the gain device for lowering the potential impressed on the grid of the gain gain, and means controlled according to the space current'of said gain device for governing the rate of gain eifected by the gain device under control of the gain'increasing means. 7 v s 16. In a signal system, a transmission line, a three-element vacuum tube gain control device connected to the line for controlling the-volume of the transmitted signals, means for impressing a potential on the grid of said gain control device according to the energy volumeon the line beyond the gain control device to limit the gain, gain increasing means comprising a gas-filled space discharge device controlled according to the energy volume on the line before the gain control device and a relay controlled by the gas-filled tube gainefiected by the gain control device under control of the control means.

for increasing the gain bysaid gaincontrol device if the energy level on the line before the gain device exceeds the peaksof the weakest talkers and the'energy level on the line 'beyond'the gain level, means in output circuit of said gas-filled tube for oftrolling said gain control devices according to the energy volume on the transmitting channel, and means for limiting the gain in the receiving chanto effect changes in gain by different-amounts by 'theitwo gain control devices under control of said control means when a strong talker ison the transmitting channel.

18. In a'transmission system, transmitting and V receiving channels, a three-element vacuum'tubje gain control device connected in series with the nel by the gain control device connected thereto transmitting channel, a three-element, vacuum tube gain control device connected across the receiving channel, a resistance element shunted across the gain control: device connected across the receiving channelfor limiting the gain by said device to effect operation of the two gain control devices by different amounts, and means for simultaneously controlling the grid potentials of said devices in accordance with the energy volume present at a point on one of said channels.

19. In a signal system, a transmission line, a gain control device connected to the line for controlling the volume of the signals, a condenser, means for controlling said deviceaccording to the charge on the condenser, control means gove erned according to the energy volume of said line for controlling the charge on said condenser line, and means for to increase the gain on the automatically varying the rate of charge on said condenser according to the operation of said device. 7

STEPHEN DOBA, JR. 

